Treesearch

Regression sampling is widely used in natural resources management and research to estimate quantities of resources per unit area. This note brings together results found in the statistical literature in the application of this sampling technique. Conditional and unconditional estimators are listed and for each estimator, exact variances and unbiased estimators for the variances are offered.

The sawtimber potential of 12-year-old Eucalyptus saligna Sm. trees grown in Maui, Hawaii, was studied by using simple field techniques. Lumber manufactured from the trees was predominantly of low grade, but had lower average density than wood from older trees, and therefore was more desirable. Logs end-split badly, and sawed with the usually encountered amount of difficulty due to growth stress that averaged 1,350 psi per log. The wood shrank moderately in drying, but lumber degrade was not serious. Bending strength, except for modulus of elasticity, was high for the specific gravity. The...

Television public service directors in California were asked to rate fire prevention film spots they had received from the California Division of Forestry. Most directors recalled receiving the spot announcements and rated them high in technical quality and interest. Delivery of the films by a fire prevention officer impressed directors favorably. Fire prevention announcements generally ranked low in likelihood of selection for showing, however. Showing might be increased by giving the announcements a local flavor; tying them in with public health, conservation, and the environment; and...

In southern California, many fires start and burn under conditions that permit their control with little burned acreage and fire damage. In contrast, under other conditions of weather and topography, on a small group of fires, control effort is relatively ineffective; they become large and destructive. A major reason for these "conflagration fires" is the extreme difficulty of stopping the head of a hot, fast-running fire in dry fuels and strong winds. No radically new concept of suppression can be anticipated. The best prospect for alleviation of the problem is modification of the...

A new procedure for constructing one-sided truncated sequential t-tests and its application to natural resource sampling are described. Monte Carlo procedures were used to develop a series of one-sided truncated sequential t-tests and the associated approximations to the operating characteristic and average sample number functions. Different truncation points and decision boundary patterns were examined. The fixed sample size t-test and Barnard's open one-sided sequential t-test were compared with the new procedure. The upper one-sided test described can easily be modified to a lower...

Progenies of nine ponderosa pines native to one granitic and several ultramafic soils in the northern Sierra Nevada were grown on both soil types in a greenhouse. The progenies differed markedly in first-year growth on infertile ultramafic soils, but not on a fertile granitic soil. Growth differences between progenies were primarily related to differences in calcium uptake from soils low in available calcium. On an extremely infertile ultramafic soil, progenies differed in survival. The results suggest that some ponderosa pines are better adapted than others to the nutritional conditions...

White fir and red fir seed collected over a 2-month period in northern California was tested for germination of fresh and stratified seed. Ratio of embryo length to embryo cavity length was found to be the most useful index of seed maturity for white and red fir. Cone specific gravity also was correlated with nearly all measures of seed germination. Data suggest that red fir cones should be collected as close to beginning of seed fall as possible. White fir cones should be collected within 3½ weeks of seed fall. White fir cones collected 4 weeks before seed fall can be artificially...

The data necessary for fire simulation may be made available through an algorithm based on tracing of boundaries composed of straight-line segments. Useful assumptions are that if a closed boundary does not contain a given point, then any other closed boundary contained within the former one does not contain the location; and that a given location will be contained in a closed boundary if the number of intersections of a finite line segment, drawn from the location to a known point inside the closed boundary, is even. The method described is similar in accuracy to existing alternative...

Control of solar light and heat to develop the proper growth environment is a desirable goal in forest management. The amount of sunlight and heat reaching the surface is affected by shadows cast by nearby objects, including trees. In timbered areas, the type of forest management practiced can help develop desired microclimates. The results depend on the size and orientation of openings created and on the shade cast by surrounding vegetation. A computerized method to calculate the extent of boundary shading for any combination of date, slope, and aspect between 23.45° N. latitude and 50°...